In recent years, mobile phones, portable cameras, notebooks, digital cameras, personal digital assistants (PDAs), CD players, as well as other portable electronic devices, are becoming popular owing to their lightweight and small size. As a consequence, batteries used to power these portable devices have also become the focus of public concern. There are different types of batteries, including dry batteries, alkaline batteries, nickel-hydrogen batteries, etc. In the following, a brief introduction is given to the most commonly adopted batteries, and in particular, to their negative electrode materials.
The zinc-manganese battery, also known as the zinc-carbon battery, is one of the most common types of dry batteries. The key feature for a typical such battery is that there is a cylindrical zinc pot surrounding the negative pole for the storage of chemicals, such as the electrolyte solution.
Within typical nickel-hydrogen batteries, hydrogen storage alloy is adopted as the negative electrode material, which plays a key role in the electricity releasing performance of such batteries.
In a fuel cell, the electrolyte substance, serving as the filter for moving ions, is filled in-between the porous positive electrodes and the negative electrodes. To ignite the desired chemical reaction, normally the positive and the negative electrodes would need the supply of air (oxygen) and hydrogen, respectively.
Although some new types of zinc-carbon batteries, alkaline batteries, and secondary batteries are allegedly environment-benign, they in fact largely contain substantial amounts of mercury and other heavy metals, such as the cobalt. Other than that, environmental pollutants are frequently used or released during the manufacturing processes of such batteries.
Lithium batteries, though widely adopted as the largest energy content among portable batteries, are unstable in the electrochemical reactions. In the worst case, explosions occur due to thermal runaway as the result of operating at low load or under improper assemblage. Therefore, multiple and complex protection mechanisms would need to be implemented for their usage, such as the installation of a protection circuit, an exhaust vent, and separation membranes, etc.
The price of the lithium batteries rises rapidly as a result of the depletion of lithium mineral, which is the main raw material of the positive electrode (such as Li1-xCoO2) and the negative electrode (such as LixC) of lithium batteries. Furthermore, the performance and life of the lithium batteries decrease rapidly within a high temperature environment.